"No garden, however small," the late Lord Rothschild is said to have once advised an audience of City horticultural enthusiasts, "should contain less than two acres of rough woodland." Of course, his lordship is absolutely right in principle, but in practice most of us have to make do with a shrub or two and a little patch of green we call the lawn.
Grass is a very common and successful plant. In many parts of the world there are vast plains entirely covered with it, and here in Ireland we have some 24,000 square miles - enough presumably, even to satisfy Lord Rothschild. That time of year has come when all this grass begins to thrive again.
Grass ceases to grow in wintertime because the temperature is low. The important temperature is that of the soil which holds the roots, but the critical conditions are known to coincide closely with an air temperature of about 5 C. Below this value there is no growth at all; above 5 degrees, the warmer it is the faster the grass grows until the temperature reaches about 10 degrees; at 10 C growth is at a maximum and any further rise in temperature has little effect.
In this way, temperature dictates the length of the growing season. Throughout most of Ireland the growing season normally starts in early to mid-March, and provided there is enough moisture, the grass grows almost continuously until mid-December. Inland Ulster has the shortest season - from late March to mid-November, and the longest growing season occurs in a narrow strip on the south and south-west coasts of Munster, where already, no doubt, the vernal surge is evident.
An adequate supply of moisture is necessary, but it does not greatly affect the rate of growth, or the amount of grass produced. Of more importance in this context is sunshine, because direct radiation from the sun facilitates the process of photosynthesis by which the plant absorbs carbon dioxide to generate new material. Cloudy weather, therefore, means less growth; it has been estimated that the volume of grass produced in Ireland would increase by some 30 per cent if our skies were perpetually clear.
It is, of course, a figure so hypothetical as to be quite meaningless. None the less, our grass is an important national assess. As the King of Brobdingnag remarked to that intrepid but singularly wreckprone traveller, Lemuel Gulliver, "Whoever could make two blades of grass to grow upon a spot of ground where only one grew before would deserve better of mankind, and do more essential service to his country, than the whole race of politicians put together."